The major structural proteins of murine mammary tumor virus: Techniques for isolation

We have utilized a variety of techniques of virus solubilization and protein separation for the isolation of the major structural polypeptides of murine mammary tumor virus, a B-type oncornavirus. Of these techniques, two isolation protocols proved to be effective and are reported here. In the first method, allowing the simultaneous purification of RNA-directed DNA polymerase and four major structural polypeptides (gp68, gp55, p28, and p12), the virions are disrupted with a nonionic detergent, and the solubilized proteins are separated by ion-exchange chromatography on DEAE- and phosphocellulose; final purification is achieved by molecular sieving chromatography. The second technique involves the solubilization of viral proteins with sodium dodecyl sulfate and chromatography on Sephadex G-200. The latter method is efficacious for the isolation of gp55, gp34, p28, and p12 after removal of the ionic detergent on Dowex columns, followed by final purification by molecular sieving chromatography.